Mobile terminal devices such as mobile telephones, smart phones, etc. which have a wide variety of applications for providing various services and functions have in recent years become widespread. And, in order to enhance the convenience by applications, there has been a demand for a linkage between the mobile terminal devices and other devices. Therefore, an in-vehicle device and a communication control method have been proposed which allow the in-vehicle device to use a service and a function by execution of an application in a mobile terminal device, by means of the linkage (Patent Literature 1).